1. Field of the Invention
This invention relates to a load port provided adjacent a semiconductor fabrication apparatus in a clean room.
2. Description of the Related Art
In a fabrication process of semiconductors, processing of a wafer in a clean room is carried out in order to achieve a high yield and high quality. However, in this day of advanced high integration of devices, enhanced refinement of circuits and enhanced increase in size of wafers, it is difficult in terms of the cost and the technique to manage fine dust in an entire clean room. Therefore, in recent years, as a method to be used in place of the improvement in cleanness in the entire clean room, a countermeasure of introducing a “mini environment system” wherein the cleanness is improved only in a local space around a wafer to carry out transportation of and other processes for the wafer is adopted. In the mini environment system, a containment called FOUP (Front Opening Unified Pod) for transporting and storing a wafer in a highly clean environment and a load port which is an apparatus at an interface section for transferring a wafer in the FOUP to and from a semiconductor fabrication apparatus and transferring the FOUP to and from a transporting apparatus are utilized as significant apparatus. In short, while a high degree of cleanness is maintained in the clean room, particularly in the FOUP and the semiconductor fabrication apparatus, a low degree of cleanness is used in the space in which the load port is disposed, or in other words, used outside the FOUP and the semiconductor fabrication apparatus, so that the cost for construction and operation of the clean room is suppressed.
Further, in a state wherein a door section provided on the load port is kept in close contact with a door provided on the rear face of the FOUP, the door section and the door are opened at the same time and the wafer in the FOUP is supplied into the semiconductor fabrication apparatus. Thereafter, the wafer is subjected to various processes or workings and then accommodated from within the semiconductor fabrication apparatus back into the FOUP.
Incidentally, while the inside of the semiconductor fabrication apparatus is kept in a predetermined gas atmosphere suitable for processing or working of a wafer, when the wafer is to be fed out from within the FOUP into the semiconductor fabrication apparatus, the internal space of the FOUP and the internal space of the semiconductor fabrication apparatus are brought into communication with each other. Accordingly, if the environment in the FOUP is lower in cleanness than in the semiconductor fabrication apparatus, then the gas in the FOUP possibly advances into the semiconductor fabrication apparatus and has a bad influence on the gas atmosphere in the semiconductor fabrication apparatus. Also there is another subject that, when the wafer is accommodated from within the semiconductor fabrication apparatus into the FOUP, an oxide film may be formed on the surface of the wafer with water, oxygen or some other gas in the gas atmosphere in the FOUP.
Thus, Japanese Patent Laid-Open No. 2006-351619 discloses a load port which places the inside of the FOUP into a gas atmosphere same or substantially same as that in the semiconductor fabrication apparatus before the internal space of the FOUP and the internal space of the semiconductor fabrication apparatus are communicated with each other. To this end, the load port is configured such that, when it is detected that a FOUP in which a wafer is accommodated is placed on a receiving plate of the load port, predetermine gas such as, for example, nitrogen gas or inert gas is introduced into the FOUP to replace the gas atmosphere in the FOUP into a predetermined gas atmosphere.
Also a mode is known wherein a purge apparatus for introducing predetermined gas such as nitrogen gas or dry air into a FOUP to replace the gas in the FOUP into the predetermined gas is provided separately from a load port. After the inside of the FOUP is replaced into the predetermined gas atmosphere by the purse apparatus, the FOUP is transported to the load port so that later processes are carried out.